Since the publication of Heincke's classic treatise on the herring the counting of vertebrae has become a standard operation in the biometric analysis of samples of teleostean fishes taken at random from local populations. But while such routine counting has undoubtedly added greatly to our knowledge of the incidence and magnitude of vertebral variation in a number of economically important species, it has occasioned no little confliction of opinion as to the significance of this variation. Difficulties arising out of my own work on the herring at Plymouth have led me to make a general study of the teleostean backbone in as many species as possible, in an endeavour to learn more of the nature, extent and cause of vertebral variation. After examining over one hundred species, mostly from local waters, I have come to the conclusion that the subject presents a great and varied field of research which is at present but little explored. It would be idle to suggest, therefore, that the present paper should be considered as anything more than an introductory survey of the many problems awaiting detailed investigation. Even so, it may serve to indicate the scope and present position of the Plymouth studies, and prepare the way for fuller work in the future, both at Plymouth and elsewhere.

I have received the greatest assistance from Mr L. S. Wisdom, Laboratory Attendant at the Plymouth Laboratory, whose skill in preparing skeletons for study, and keen interest in all matters relating to the research, I most gratefully acknowledge.

The development of the hydroid of Amphinema dinema (Peron & Lesueur) has been followed in the laboratory until the production of young medusae and the hydroid identified as Perigonimus serpens Allman.

The hydroid of Amphinema rugosum (Mayer) is described for the first time. It is very similar to P. serpens but more robust.

The hydroid has been reared from Rathkea octopunctata (Sars); it is very minute and the hydranths possess a single whorl of long filiform tentacles/

A small Cuspidella hydroid was reared from Mitrocomella brownei (Kramp).

Certain points in the synonymy of these species are discussed. An account of the methods of rearing used is also given.

Wimpenny's measurements of Rhizosolenia styliformis (this Journal, Vol. xxi, pp. 29-60,1936) are used to discuss the value of population curves of this species as indicators of water movements and mixture in the North Sea. His alleged correlation between average size and temperature is shown in this case to be untenable. On the coastal banks during 1933 there was a steady increase of size accompanying normal regeneration (bimodal curves), but this was complete by November, and in 1934, with fuller seasonal sampling, the size steadily diminished (all curves unimodal). The population phases on the Dogger and coastal banks were markedly divergent in 1933, but almost identical and intermixed in 1934, indicating a northern (“Atlantic”) influx in 1933 and its absence in 1934. Off the southern edge of the Dogger in the autumn of 1932 a bimodal and unimodal population were variously mixed, the former showing relations to the coastal population of the following spring, the latter probably marking the intrusive northern element which persisted into 1933.

The rates at which Calanus finmarchicus eat both carmine particles and the diatom Nitzschia closterium have been investigated by Fuller & Clarke (1936) and Fuller (1937). They found that the number of Nitzschia or of carmine particles, eaten by a Calanus in unit time, was proportional to the concentration of Nitzschia or of particles in the water. Lucas (1936) also found that Neomysis and Eurytemora ate Nitzschia at rates which were roughly proportional to the concentration of diatoms in the water over fairly wide limits.

During 1935 I had made, as part of another investigation, three experiments on the rate at which Calanus eat diatoms of larger size. This happened much more rapidly than Fuller found to be the case with suspensions of Nitzschia. Meanwhile Lowndes (1935) had concluded, from direct observations, from the anatomy of their mouth-parts and from observations by Lebour and Marshall, that Calanus should be able to catch and select food. He concludedthat Calanus does not depend entirely upon its (automatic) filtering mechanism for all the food it obtained.

The quantitative data which I had collected in these three experiments, in conjunction with those published by Fuller & Clarke (1936,1937), were suitable for examining this contention. They suggested that the animal when fed with diatoms of moderate size selected by catching the species it preferred, while it automatically filtered the minute Nitzschia. With these possibilities in view, experiment N 90 was made in order to link up the three experiments with the numerous experiments made by Fuller (1937).

On February 29 1937 the larvae of Spirontocaris spinus var. lilljeborgi were hatched out in the Dove Marine Laboratory by Dr H. O. Bull and sent to me for examination. As the larvae differ in certain important points from those of other species known and there is no published account of them, it seems worth while giving a short description, although the later larvae have not been identified and it was not possible to rear them further.

Molluscs are very important members of our marine fauna, and, since many of them are planktonic in their early stages, they contribute largely to the number of organisms available as food for plankton-eating animals. The present work includes the prosobranchs only, particularlythose from Plymouth which have been specially studied during the last few years. Several papers have already been published dealing with the Plymouth species (Lebour, 1931–6), and these are referred to in due course. The present paper brings together the above work and that of others and summarizes our knowledge of the larval prosobranchs of Britain, with a description of the eggs. Naturally there are still many gaps, but it is hoped that these may be filled in time. A preliminary paper on the subject has already appeared (Lebour, 1933f). Closely related foreign species are referred to for comparison with our British forms. Original notes on certain species and information on the echinospira larva of Capulus ungaricus are given here for the first time. Figures of typical eggs and larvae are given.

The activity of oxygen in sea water and standard oxygen electrode potentials at a range of temperatures have been computed.

Accurate values for the thermodynamic ionic product of water, Kw, found by Harned & Hamer, have been applied to the calculation of the activity of hydroxyl ion in sea water from pH measurements.

The activity of water in sea water has been computed from the lowering of the freezing-point.

From these data the theoretical reversible oxidation-reduction potential of sea water has been calculated.

.Typical data for the irreversible potential in the pH range 1-8 have been derived from Hoar's results with which experimental determinations made by Dr Atkins agree. Thus the oxidation-reduction potential of sea water is controlled solely by the oxygen system.

Data are presented confirming the belief of Harvey and of Redfield that, in broad outline, the ratio of nitrate-nitrogen and of phosphate-phosphorus in the sea and of nitrogen and phosphorus in marine plankton lies within fairly narrow limits. The ratio approaches twenty to one when expressed in terms of milligram-atoms or nine to one by weight. There are however deviations from this broad generalization, but they do not provide a reason for discarding the concept but rather suggest close examination of the causes of the variations.

The nitrogen cycle in the sea is reviewed as a whole in accordance with the scheme set out in Fig. 1. This summary includes only original matter, since the survey of other work does not admit of further condensation. The metabolism has been discussed of the following sources of nitrogen available to plants in sea water: mono, di and trimethylamine, trimethylamine oxide, urea, amino-acids, ammonia, hyponitrite, nitrite and nitrate. The methylamines will interfere in analyses of ammonia by distillation. Thermodynamic methods have been extensively used. The equilibrium between urea and ammonium cyanate at sea-water concentrations favours the cyanate. In sea water containing 28 mg. ammonia N per cu. m., the equilibrium mixture will contain fifteen times as much cyanate as urea. Hydrolysis of urea is probably purely chemical.

The nature of iron occurring in sea water, and its utilization by diatoms, is discussed.

Diatoms in the sea obtain many thousand times more iron than calculation shows they can obtain by diffusion of iron ions from the surrounding water.

Evidence is presented that ferric hydroxide is readily adsorbed on the surface of diatoms.

It is shown that colloidal and larger particles of ferric hydroxide or phosphate can be utilized by, and support the growth of diatoms.

Experiments show that the diatoms Nitzschia closterium and Lauderia borealis require, for continued growth, a very small quantity of iron compared with that found on, and in, diatoms taken from the open sea.

It is contended that iron hydroxide adsorbed on diatoms is in contact with an interface where its solution, and subsequent passage into the cell, is probable.

Colloidal ferric hydroxide flocculates in sea water, the less rapidly the greater the dilution. When formed in the presence of very small quantities of various emulsoids, it does not flocculate on adding to sea water or flocculates less rapidly.

The question is raised how pelagic larvae of marine bottom animals reach a type of substratum suitable for adult life. Attention is drawn, to a few forms in which it is not entirely due to chance, since their larvae have been shown to exercise some degree of choice of the soil on which they will settle, and to be capable of preserving the ability to metamorphose for several days at least. These powers, if found to be fairly general in marine bottom animals, would have important bearings on distribution problems. There is supporting evidence from the investigations of Notomastus latericeus Sars here described. The adult is found in mud or muddy sand. Experiments showed that larvae of this species if provided with mud or sand generally metamorphose several days before those kept in clean glass vessels or with clean shell gravel. Mud perhaps induces slightly more rapid settling than sand. After metamorphosis the growth and health of the young worms is generally much better in mud or sand than in gravel or clean glass vessels.

1. Samples of herring from the Clyde sea-area were obtained weekly from the time of hatching in March until metamorphosis in June.

2. The rate of growth was regular, about 3 mm. in length per week; the development was similar to that described from elsewhere.

3. The herring which hatched off the south-west of Arran gradually moved northwards into the mouth of Loch Fyne and remained there until metamorphosis.

4. The proportion feeding was usually small. The food consisted mainly of copepods, both young stages and adults. The size of the food organisms eaten depended roughly on the size of the herring

The sodium, potassium, calcium, iron and copper have been determined in sixteen marine gastropods, and the results are briefly discussed. A noteworthy finding is the large amount of potassium, calcium and (or) magnesium which may be present in these animals. Lacuna vincta for example may contain over I-I % of potassium, Archidoris britannica 1-58 % of magnesium per 100 g. of live weight

The body of Archidoris britannica contains very high concentrations of calcium and magnesium which appear to be combined mostly with CO3 and fluoride. The bulk of these materials are in solid deposits throughout the submucous tissue. Sodium chloride and potassium phosphate account for most of the residual mineral matter.

The mucus secreted by the body has an inorganic composition resembling sea water.

The visceral mass contains only one-tenth as much calcium and magnesium as the body. The predominating bases are potassium and sodium and the acid radicles are essentially chlorides and phosphates.

A study has been made of the seasonal and other variations in the contents of fat, water and total solids (other than fat) of the flesh of herring. The herring studied were mainly from Scottish and Shetland waters.

Various races of herring, differing anatomically and with different spawning seasons, are considered separately.For each, the observed changes in chemical composition are considered in relation to the season of the year and the feeding and spawning cycles of the fish.

During May and June there is a rapid rise in the fat content of herring (demonstrated for some races and inferred for the rest). This is correlated with a period of intensive feeding. After the attainment of maximal values in July there is a fall to minimal values in April. The rapidity of the fall depends on the spawning season, a relatively high fat content being maintained until spawning takes place. During spawning there is a rapid fall in the fat content, due, in part at least, to cessation of feeding.

The importance of killing contractile animals in an expanded condition cannot be over-estimated. A glance at the immense confusion and uncertainty which prevails in several branches of tropical marine invertebrates, and in particular the Coelenterata, will give a clear picture of the value of good preservation. Killing contractile animals in an expanded condition has always offered considerable difficulty. Several methods have been recommended for different animals, but it is often very difficult to choose the appropriate one, since animals belonging to one and the same group may behave quite differently towards any method. The writer, during his work for the last three years at the Marine Biological Station of the University of Cairo at Ghardaqa in the Red Sea, has taken great pains to preserve a variety of marine invertebrates as fully expanded as possible. Some of the successful results and the methods used are therefore given here.

The commonest method for the present purpose is the use of narcotics. The most familiar of these are menthol, chloral hydrate, alcohol, magnesium sulphate and cocaine. Owing to the difficulty in obtaining cocaine it cannot be freely used for general purposes. Menthol enjoys a great reputation for narcotization which, in fact, it does not quite deserve. Although in some few cases it gave good results, yet in the majority it was quite unsatisfactory, as delicate animals begin to macerate before they are properly narcotized. It is generally applied in the crystal form and sprinkled on die surface of the water. Apparently its low solubility is responsible for a great many of its failures.

1. A method, due to Poole & Atkins, is described for computing the total available energy at any depth in the sea, in joules or g.-cal.

2. The oxygen production of pure cultures of the diatom Coscinodiscus excentricus Ehr. was measured by the Winkler method after exposure of the diatoms in bottles at known depths in the sea. 3. The results of simultaneous measurements of oxygen production and of energy are given for 6 days in July and August 1933 and 1934.

4. Factors, other than light, that might affect the rate of oxygen production in the experiments are discussed and shown to be negligible. It is assumed that diatoms can use energy for photosynthesis equally well in all parts of the visible spectrum.

5. When the energy flux during the exposures is less than 75 joules or i-8 g.-cal. per cm.2 per hr., the oxygen production is directly proportional to the energy. The utilization of the available energy then amounts to about 7%.

Comparison of the methods of adhesion and locomotion of the typical members of the four classes of the Eleutherozoa reveals a similarity of the adhesive mechanism in the Asteroidea, Echinoidea and Holothuroidea in that adhesion is due in part to suction and in part to the secretion of mucus. The ophiuroid, on the other hand, has tube feet which, because of their lack of a well-defined sucker, must adhere merely by their intrinsic stickiness. The ability to make use of suction results from the possession of a sucker so fashioned that the median part of the disk may be withdrawn from the surface of contact, with the resultant production of a vacuum. The sucker of the asteroid, echinoid or holothurian tube foot is well adapted for this purpose. An essential feature of such a disk is the presence of an arborescent system of connective tissue fibres extending from the basal plate to the outer limit of the ectoderm. By means of this system, the pull initiated by contraction of the longitudinal musculature of the podium is transmitted to the ectoderm of the sucking disk, the central part of which is thereby lifted up. Where suction plays no part in adhesion, as in the Ophiuroidea, the arborescent system of fibres is lacking.

1. Dead marine diatom plankton was found to undergo rapid oxidation and decomposition when added to fresh sea water. This was measured by oxygen consumption, nitrogen liberation, phosphate regeneration and bacterial multiplication.

2. Living diatoms added to sea water and placed in the dark continued to absorb oxygen; they were rather resistant to bacterial attack.

3. Diatom-rich marine plankton also absorbed oxygen, while the phosphorus was gradually regenerated. The bacteria did not increase in numbers in correspondence with the oxidation of the fresh diatom material.

4. When sea water in which photosynthesis was allowed to proceed for varying periods of time was placed in the dark, rapid oxidation of the freshly synthesized material took place, as indicated by oxygen consumption and phosphate liberation. Although there was a greater number of bacteria in the water in which photosynthesis took place, the oxidation of the fresh diatom material was not accompanied by any large increase in bacteria; in fact a decrease in numbers was frequently observed.